Classifications

• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61K—PREPARATIONS FOR MEDICAL, DENTAL OR TOILETRY PURPOSES
  • A61K8/00—Cosmetics or similar toiletry preparations
  • A61K8/18—Cosmetics or similar toiletry preparations characterised by the composition
  • A61K8/30—Cosmetics or similar toiletry preparations characterised by the composition containing organic compounds
  • A61K8/40—Cosmetics or similar toiletry preparations characterised by the composition containing organic compounds containing nitrogen
  • A61K8/44—Aminocarboxylic acids or derivatives thereof, e.g. aminocarboxylic acids containing sulfur; Salts; Esters or N-acylated derivatives thereof
  • A61K8/447—Aminocarboxylic acids or derivatives thereof, e.g. aminocarboxylic acids containing sulfur; Salts; Esters or N-acylated derivatives thereof containing sulfur
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q13/00—Formulations or additives for perfume preparations
• • A—HUMAN NECESSITIES
  • A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
  • A61Q—SPECIFIC USE OF COSMETICS OR SIMILAR TOILETRY PREPARATIONS
  • A61Q15/00—Anti-perspirants or body deodorants

Definitions

• the present invention relates to an improved method and apparatus for preparing low-concentration poiysilicate microgels, i.e., aqueous solutions having an active silica concentration of generally less than about 1.0 wt.%, which are formed by the partial gelation of an alkali metal silicate or a poiysilicate, such as sodium poiysilicate, having in its most common form one part Na2 ⁇ to 3.3 parts Si ⁇ 2 by weight.
• the microgels which are referred to as "active" silica in contrast to commercial colloidal silica, comprise solutions of from 1 to 2 run diameter linked silica particles which have a surface area of at least about 1000 m ⁇ /g.
• the particles are linked together during preparation, i.e., during partial gelation, to form aggregates which are arranged into three- dimensional networks and chains.
• the poiysilicate microgels can be further modified by the incorporation of aluminum oxide into their structure.
• Such alumina modified polysilicates are classified as polyaluminosilicate microgels and are readily produced by a modification of the basic method for poiysilicate microgels.
• a critical aspect of the invention is the ability to produce the microgels within a reasonable time period, i.e., not longer than about 15 minutes until the microgel is ready for use, without the risk of solidification and with minimum formation of undesirable silica deposits within the processing equipment.
• Poiysilicate microgels produced according to the invention are particularly useful in combinations with water soluble cationic polymers as a drainage and retention aid in papermaking.
• these products are more appropriately referred to as polysilicic acid microgels.
• these products can contain mixtures of polysilicic acid and poiysilicate microgels; the ratio being pH-dependent.
• poiysilicate microgels are particularly useful in combinations with water soluble cationic polymers as a drainage and retention aid in papermaking.
• the silica concentration of the water soluble silicate starting solution is in the range of from 2 to 10 wt.% silica
• the concentration of the strong acid e.g., sulfuric acid
• the preferred conditions in the mixing zone are a Reynolds number greater than 6000, a silica concentration in the range of 1.5 to 3.5 wt.% and a pH in the range of 7 to 10.
• the most preferred conditions are a Reynolds number greater than 6000, silica concentration of 2 wt.% and a pH of 9.
• alumina modified microgel is best conducted by adding a soluble aluminum salt to the acid stream in an amount ranging from about 0.1 wt.% up to the solubility limit of the aluminum salt.
• the most useful polyaluminosilicate microgels are those prepared with an Al2 ⁇ 3/Si ⁇ 2 mole ratio ranging from 1 : 1500 to 1:25 and, preferably, from 1:1250 to 1:50.
• the apparatus comprises: (a) a first reservoir for containing a water soluble silicate solution; (b) a second reservoir for containing a strong acid having a pKa of less than 6; (c) a mixing device having a first inlet which communicates with said first reservoir, a second inlet arranged at an angle of at least 30 degrees with respect to said first inlet which communicates with said second reservoir, and an exit; (d) a first pumping means located between said first reservoir and said mixing device for pumping a stream of silicate solution from said first reservoir into said first inlet, and first control means for controlling the concentration of silica in said silicate solution while said solution is being pumped such that the silica concentration in the exit solution from the mixing device is in the range of 1 to 6 wt.%; (e) a second pumping means located between said second reservoir and said mixing device for pumping a stream of acid from said second reservoir into said second inlet at a rate relative to the rate of said first pumping means sufficient to produce a Reynolds number
• the apparatus of the invention includes a NaOH reservoir and means for periodically flushing the production system with warm NaOH which has been heated to a temperature of from 40 to 60°C whereby deposits of silica can be solubilized and removed.
• an agitating gas stream such as a stream of air or nitrogen or other inert gas can be introduced into the mixing device described by means of an additional inlet located at or near the mixing junction.
• Gas agitation provides an important industrial benefit in that it permits low silicate flow rates to be employed while maintaining the required turbulence and Reynolds number in the mixing zone.
• mixing of the acid, aluminum salt and the water soluble silicate solution can be accomplished in an annular mixing device.
• This device can be an internal pipe or tube which protrudes into and subsequently discharges inside of a larger pipe or tube.
• the internal pipe discharge point is usually, but not necessarily, concentrically located inside the external pipe.
• One of the two fluids to be mixed is fed into the internal pipe.
• the second fluid is fed into the external pipe and flows around the outside of the internal pipe. Mixing of the two fluids occurs where the first fluid exits the internal pipe and combines with the second fluid in the larger external pipe.
• the acid and the aluminum salt solution are premixed prior to being fed into one of the pipes.
• the water soluble silicate solution and the acid can be fed to either the internal or the external pipes at rates sufficient such that when the two streams are combined, a Reynolds number of greater than 4000 is produced in the mixing zone.
• An agitating gas stream can also be optionally employed to aid in the mixing of the two streams.
• mixing of the acid and water soluble silicate solution can be accomplished in a vessel equipped with mechanical means to create the necessary turbulence, such that mixing of the two streams is accomplished at a Reynolds number of greater than 4000.
• the vessel can optionally be equipped with baffles.
• the acid and water soluble silicate solution can be but do not have to be fed to the vessel simultaneously.
• a concentrated solution of an aluminum salt preferably aluminum sulfate
• an aluminum salt preferably aluminum sulfate
• the rate of formation of microgel is increased and a polyaluminosilicate microgel is formed having aluminum moieties incorporated throughout the microgel structure.
• the method and apparatus of the invention are capable of producing stable poiysilicate and polyaluminosilicate microgels resulting in reduced silica deposition within a convenient time frame of not more than about 15 - 16 minutes, but usually within 30 to 90 seconds, without the risk of solidification and with minimum formation of undesirable silica deposits within the processing equipment.
• Temperature of operation is usually within the range of 0-50°C.
• Silica deposition in production apparatus is undesirable because it coats all internal surfaces of the apparatus and can impede the functioning of vital moving parts and instrumentation. For example, silica deposition can build to the point where valves can no longer function and can restrict fluid flow through pipes and tubing. Deposition of silica is also undesirable on the pH sensing electrode as it prevents monitoring the process pH, a critical quality control parameter for silica microgel production.
• Fig. 1 is a schematic diagram of the process which includes a NaOH reservoir and means for periodically flushing the production system.
• Fig. 2 is a schematic diagram of a dual line poiysilicate microgel production system which provides for uninterrupted microgel production.
• Fig. 3 is a schematic diagram of the process of the invention for the production of polyaluminosilicate microgels which includes an aluminum salt reservoir and means for introducing said salt into the dilute acid stream.
• Active silica is a specific form of microparticulate silica comprising very small 1-2 nm diameter particles which are linked together in chains or networks to form three-dimensional structures known as "microgels".
• the surface area of the active silica microparticUlates, i.e., the microgels, is at least about 1000 m ⁇ /g.
• General methods for preparing poiysilicate microgels are described in U.S. Patent 4,954,220, the teachings of which are incorporated herein by reference.
• the acidification of a dilute aqueous solution of an alkali metal silicate with an inorganic acid or organic acid, i.e., a strong acid having a pKa of less than 6, is the method to which this invention is particularly applicable.
• the present invention provides for the reliable and continuous preparation of low-concentration poiysilicate and polyaluminosilicate microgels at the site of intended consumption without formation of undesirable silica deposits within the processing equipment and at very reasonable aging times generally less than 15 minutes, and preferably between from 10 to 90 seconds.
• the method of the invention is carried out by simultaneously introducing a stream of a water soluble silicate solution and a stream of strong acid having a pKa less than 6, along with an aluminum salt, into a mixing zone or mixing junction such that the streams converge at an angle of generally not less than 30 degrees, with respect to each other and at a rate which is sufficient to produce a Reynolds number in the region where the two streams converge of at least 4000, and preferably in the range of about 6000 and above.
• Reynolds number is a dimensionless number used in engineering to describe liquid flow conditions within a tube or pipe. Numbers below 2000 represent laminar flow (poor mixing environment) ' and numbers of 4000 and above represent turbulent flow (good mixing environment). As a general rule, the larger the Reynolds number the better the mixing. Reynolds number, (Re) for flow in a pipe or tube, is determined from the equation
• N Rotational velocity in revolutions per second
• p Fluid density in grams per cm ⁇
• u Viscosity in grams per (second)(centimeter)
• the concentrations of the converging silicate solution and the acid/aluminum salt streams are controlled so that the resulting silicate/acid mixture thus produced has a silica concentration in the range of 1 to 6 wt.% and a pH in the range of 2 to 10.5. More preferably the silica concentration is in the range of 1.5 to 3.5 wt.% and the pH is in the range of 7 to 10.
• the most preferred operating conditions are with a Reynolds number larger than 6000, a silica concentration of 2 wt.% and a pH of 9.
• Aging is generally accomplished in from 10 up to about 90 seconds by passing the silicate/acid mixture through an elongated transfer loop in route to a finished product receiving tank in which the mixture is immediately diluted and thereafter maintained at an active silica concentration of not greater than 2.0 wt.% and, preferably, not greater than 1.0 wt.%. Partial gelation which produces the three-dimensional aggregate networks and chains of high surface area active silica particles is achieved during aging. Dilution of the silicate/acid mixture to low concentration operates to halt the gelation process and stabilize the microgel for subsequent consumption.
• Fig. 1 is a schematic diagram of the process in its simplest form to prepare poiysilicate microgels.
• the sizes, capacities and rates described herein can be varied over wide ranges depending primarily on the quantities of poiysilicate microgel required and the expected rate of consumption.
• the sizes and capacities described in reference to the drawings relate to a system for producing, i.e., generating, poiysilicate microgel on a generally continuous basis for consumption as a drainage and retention aid in a papermaking process in which the consumption rate ranges from about 10 to 4000 lbs. microgel per hour. There is shown in Fig.
• a dilution water reservoir 1-Q a dilution water reservoir 1-Q, an acid reservoir 12, and a silicate reservoir 14.
• the reservoirs i.e., tanks, are conveniently made of polyethylene, with the water reservoir having a capacity of 500 gallons, the acid reservoir having a capacity of 100 gallons, and the silicate reservoir having a capacity of 300 gallons.
• Other vessels shown in Fig. 1 are NaOH flush tank 16. and finished product receiving tank -1-&.
• the NaOH flush tank is made of a non-corrosive material, such as, for example, 316 stainless steel; it has a capacity of 20 gallons and is heated with an electrical resistance drum heater wrapped around it (Cole-Palmer, 2000 watts, 115 volts).
• the finished product receiving tank has a capacity of 1000 gallons and is made of polyethylene.
• a critical element of the process is mixing junction 20 which defines a mixing zone in which a stream of acid and a stream of water soluble silicate are introduced along individual paths which converge within the mixing zone at an angle generally not less than 30 degrees.
• a mixing "T” or " Y” junction is suitable for practicing the invention and may readily be constructed from an appropriately sized 316 stainless steel “Swagelok” compression coupling fitted with stainless steel tubing. A “T” junction is generally preferred.
• the rates at which the two streams enter, i.e. are pumped into, the mixing zone are selected to produce a Reynolds number therewithin of at least 4000 and preferably up to 6000 or higher which results in practically instantaneous and thorough mixing of the acid and silicate such that the resulting mixture has a silica concentration in the range of from 1.5 to 3.5 wt.% and a pH of from 7 to 10.
• the commercial silicate is maintained undiluted in reservoir 14, usually at a concentration of 24 to 36 wt.% as supplied by the manufacturer, until it is needed. It is supplied to the mixing junction 20 via suitable tubing 22 (316 SS, 1/4 inch OD) by means of a low flow rate gear or micropump 24 (e.g., Micropump Corp., model 140, max. flow 1.7 gpm).
• suitable tubing 22 316 SS, 1/4 inch OD
• micropump 24 e.g., Micropump Corp., model 140, max. flow 1.7 gpm.
• Non-corrosive materials of construction e.g., 316 stainless steel, are preferred to avoid any risk of corrosion and subsequent contamination.
• the silicate supply line also includes flow control valve 26 (Whitey, 316 SS, 1/4 inch needle), magnetic flow meter 28 (Fisher Porter, 316 SS, 1/10 inch size) and check valve 86 (Whitey, 316 SS, 1/4 inch diameter) for controlling and monitoring the amount and direction of silicate flow.
• flow control valve 26 White, 316 SS, 1/4 inch needle
• magnetic flow meter 28 Fisher Porter, 316 SS, 1/10 inch size
• check valve 86 Whitey, 316 SS, 1/4 inch diameter
• an in-line static mixer 32 Cold-Palmer, 316 SS, 1/2 inch tubing, 15 elements
• a check valve 30 Whitey, 316 SS, 1/2 inch diameter
• the dilution water is supplied via line 34 (1/2 inch OD, 316 SS) by centrifugal pump 36 (Eastern Pump, 1HP, max. flow 54 gpm), and a rotameter 38 (Brooks, Brass Ball, 3.06 gpm max.).
• Control valve 40 Whitey, 316 SS, 1/2 inch NE needle
• check valve 42 Whitey, 316 SS, 1/2 inch diameter
• junction mixer 20 flow 0.83 gpm to junction mixer 20 through line 46 (316 SS, 1/4 inch OD) and check valve 88 (Whitey, 316 SS, 1/4 inch diameter).
• a single loop controller 90 (Moore, Model 352E) is combined with pH transmitter 48 (Great Lakes Instruments, Model 672P3FICON) and pH Probe 48A (Great Lakes Instruments, Type 6028PO) to regulate the flow of acid to junction mixer 20 via automatic flow control valve 50 (Research Controls, K Trim, 1/4 inch OD, 316 SS) in response to the pH of the silicate/acid mixture measured at the exit of the junction mixer.
• An automatic three-way valve 52 (Whitey, 316 SS, 1/2 inch diameter) is also employed within the control system to allow for the possibility of having to divert off-spec, silicate/acid mixture to the sewer.
• Dilution water from water reservoir 1-Q is provided via line 54 (316 SS, 1/2 inch OD) to dilute the acid supply upstream of junction mixer 20 to a predetermined concentration in the range of from 1 to 20 wt.%.
• a static mixer 56 Cold-Palmer, 316 SS, 1/2 inch diameter, 15 turns) is provided downstream of the point where dilution water is introduced into the acid supply line to insure complete mixing and dilution of the acid.
• a rotameter 58 (Brooks, Brass Ball, 1.09 gpm. maximum), control valve 60 (Whitey, 316 SS, 1/2 inch needle) and check valve 62 (Whitey, 316 SS, 1/2 inch diameter) are used to control flow rate and flow direction of the dilution water.
• the silicate/acid mixture which exits junction mixer 20 has preferably a Si ⁇ 2 concentration in the range of from 1.5 to 3.5 wt.% and a pH in the range of from 7 to 10. Most preferably the silica concentration is maintained at 2 wt.% and the pH at 9.
• the mixture is passed through an elongated transfer line 64 (1-1/2 inch schedule 40 PVC pipe, 75 feet in length) in route to finished product receiving tank 1&.
• the length of the transfer line is selected to insure that the transfer will take at least 10 seconds, but preferably from about 30 seconds to 90 seconds, during which time "aging" or partial gelation of the mixture takes place. Transfer time can be as long as 15-16 minutes at very low flow rates and still produce satisfactory results.
• Dilution water from reservoir 1Q is added via line 66 (316 SS, 1/2 inch OD) to the mixture just prior to its entry into finished product receiving tank IS or at any other convenient location so long as the silicate/acid mixture is diluted to an Si ⁇ 2 concentration of less than 1.0 wt.% which stabilizes the gelation process.
• Dilution water is supplied with centrifugal pump 68 (Eastern, 316 SS, 1 HP, 54 gpm maximum), and flow control is accomplished at a predetermined rate with control valve 70 (Whitey, 316 SS, 1/2 inch needle) and rotameter 72 (Brooks, SS Ball, 12.46 gpm maximum).
• the finished product receiving tank IS is provided with a level control system 74 (Sensall, Model 502) which operates in conjunction with an automatic three-way valve 76 (Whitey, 316 SS, 1/2 inch diameter) to divert flow of the silicate/acid mixture to the sewer if the level of finished product becomes too high.
• a level control system 74 Silicone, Model 502
• an automatic three-way valve 76 White, 316 SS, 1/2 inch diameter
• Dilution water from pump 36 is then circulated through the downstream portion of the system for about 5 minutes, after which pump 36 is shut off, and the dilution water reservoir is isolated by closing valves 40, 60 and 70.
• Three- way automatic valves 52 and 76, and manual valves 78, 80 and 82 are then activated along with centrifugal circulating pump 84 (Eastern, 316 SS, 1.5HP, 15 gpm maximum) to allow NaOH, maintained at a concentration of 20 wt.% and a temperature in the range of from 40 to 60°C, to circulate through the downstream portion of the system for generally not longer than about 20-30 minutes.
• FIG. 2 there is shown a schematic diagram of a dual line production system for active silica, whereby one line can be operational at all times while the other line is being flushed or being maintained in a stand-by condition.
• the component parts are numbered in accordance with Fig. 1.
• a commercial system according to either of Figs. 1 or 2 will generally be constructed of stainless steel or polyvinyl chloride tubing of generally one inch diameter or less, depending on the requirement for active silica. When stainless steel tubing is used, connections ofthe various instruments, fittings, valves, and sections can be conveniently made with "Swagelok" compression joints.
• Fig. 3 is a schematic diagram showing a modification ofthe basic apparatus of Fig. 1 suitable for the production of polyaluminosilicate microgels.
• a concentrated solution of an aluminum salt preferably aluminum sulfate
• tubing (1/4 inch diameter 316 stainless steel)
• the metering pump 102 can be linked electronically to the controller 90 and can move in parallel with silicate usage.
• the aluminum salt solution can be introduced into the diluted acid line at the point 106 by means of a 316 SS "T" junction. Thorough mixing ofthe aluminum salt with the diluted acid can be completed by the in-line mixer 56 before reaction with the silicate, to produce polyaluminosilicate microgels, occurs at "T” junction 20.
• a preferred aluminum salt solution for use in the method is a commercial solution of aluminum sulfate such as liquid alum solution Al2(SO4)3,14H2O containing 8.3 wt.% AI2O3 supplied by the American Cyanamid Company.
• a dual line apparatus for the continuous production of polyaluminosilicate microgels can be constructed by the appropriate modifications ofthe dual line apparatus of Fig. 2.
• Example 1 Demonstrating the effect of turbulence in reducing silica deposition.
• a laboratory generator for producing poiysilicate microgels was constructed according to the principles described in Fig. 1.
• the critical junction mixer was constructed from a 1/4 inch, 316 stainless steel "Swagelok" T-compression fitting fitted with 6 inch arms of 1/4 inch OD 316 SS tubing. The internal diameter ofthe fitting was 0.409 cm.
• a similar "Swagelok" X-compression coupling was used with the fourth arm ofthe X as the gas inlet.
• An in-line filter comprised of 1 inch diameter 60 mesh stainless steel screen was placed about 12 inches from the acid/silicate junction to trap particulate silica.
• the screen was weighed at the beginning of each test and again at the end of each test, after washing and drying, so as to give a measure of silica deposition. All tests were run so as to maintain conditions of 2 wt.% silica and pH 9 at the point of silicate acidification and each test was run for sufficient time to produce a total amount of 1,590 gms. of poiysilicate microgel. The results ofthe tests are given in Table 1 below. Liquid flow represents the total liquid flow, that is, the flow ofthe combined silicate/acid mixture in the exit tube.
• a commercial sized apparatus for preparing active silica microgels was assembled according to the schematic design shown in Fig. 1 and installed in a commercial paper mill.
• the apparatus except for the raw material supply reservoirs, was rigidly mounted on steel framework on two skids each measuring approximately six feet by eight feet.
• skid 1 On skid 1 was mounted inlets for connection to commercial supplies of sodium silicate and sulfuric acid and an inlet for city water which was used for dilution purposes.
• skid 1 was mounted the dilution and flow control means, the silicate/acid mixing junction, pH measurement and pH controller, sodium hydroxide flush reservoir, required pumps and valves and the electrical controls.
• skid 2 On skid 2 was mounted the aging loop, finished product reservoir, level controller and required pumps and valves. Overall height of each skid was about seven feet.
• the manufacturers supply containers were used as reservoirs for the silicate and sulfuric acid and these were connected directly to the appropriate inlets on skid 1.
• the apparatus was operated continuously for six (6) days during which 0.5 wt.% active silica was produced at a rate which varied between 3 and 4.8 gallons per minute. At a production rate of 3 gpm, a Reynolds number of 4250 was calculated for the mixing zone employed. No silica deposition was observed within the junction mixer 20, although some silica deposition was observed in the proximity ofthe pH probe located immediately downstream from the junction mixer exit after 12 hours of continuous operation. To alleviate this situation, a water/NaOH/water flush sequence was conducted, which took less than 30 minutes, and the system was then returned to normal production. Over the entire six day period, the apparatus operated without fault and produced active silica of excellent quality which was utilized by the mill for the production of a range of papers with different basis weights.
• a commercial-sized apparatus for preparing polyaluminosilicate microgel solution was assembled according to the principles shown in Figure 3.
• the apparatus except for the raw material supply reservoirs, was rigidly mounted on steel framework on two skids each measuring approximately eight feet by eight feet.
• On skid 1 were mounted inlets for connection to supplies of sodium silicate, sulfuric acid, sodium hydroxide and papermaker's alum and an inlet for city water which was used for dilution purposes.
• Also mounted on skid 1 were the required pumps for each chemical and a reservoir for containing the finished polyaluminosilicate microgel solution.
• the apparatus was used to produce 6000 gallons of 0.5 wt% polyaluminosilicate microgel solution at a rate of 20 gallons per minute. A Reynolds number of 22,700 was calculated for the mixing zone. Only minor silica deposition was noted on the pH electrode after 5 hours of operation. To remove the silica deposits, a NaOH flush was conducted, which took less than 30 minutes, and the system was then returned to normal production. The polyaluminosilicate microgel solution was utilized by a paper mill for the production of liquid packaging board with excellent results.

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• 1995
  • 1995-10-25 US US08/548,223 patent/US5733535A/en not_active Expired - Fee Related
• 1996
  • 1996-10-16 WO PCT/US1996/016534 patent/WO1997015283A1/en active Application Filing
  • 1996-10-16 AU AU74354/96A patent/AU7435496A/en not_active Abandoned
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